Kyushu J7W Shinden

In 1943, the UN issued an 18-shi specification that included the requirement for a new inter­ceptor. Japanese aircraft tasked with inter­ception roles had by this time begun to be eclipsed by the newest Allied fighters and the IJN sought to ensure their edge was main­tained. Three contenders submitted their designs and it would be Kyushu’s that was the most radical of them all: the J7W Shinden.

The man behind the Shinden (‘Magnificent Lightning’) was Captain Masaoki Tsuruno, a member of the Technical Staff of the IJN. Tsu­runo conceived an interceptor that made use of a configuration rarely seen at the time of his design work, a design with canard fore­planes. Canards were not a new concept, even in 1943. They were seen as far back as 1910 with a Gabriel and Charles Voisin design and later a Bleriot tail-first aircraft had incor­porated canards. (Both planes used the term ‘canard’ which in French means ‘duck’ – the 1910 Canard Voisin and the 1911 Bleriot ‘Canard’). Canards would sporadically appear in experimental aircraft right up to World War 2, examples being the 1929 Raab – Katzenstein Rakate, the 1931 Focke-Wulf Ente (the ‘Duck’) and the 1937 Beltrame Col – ibri. Tsuruno felt canards could offer a num­ber of advantages such as reducing the chances of stalling, improved controllability and manoeuvrability and easing some con­struction concerns such as the engine instal­lation and control linkage arrangements.

Besides the canards, Tsuruno introduced another feature in the Shinden that was cer­tainly new to the Japanese – the use of a tur­bojet to power the aircraft. Of course, Tsuruno understood that a more conven­tional piston-engine would have to be used until such time as a suitable turbojet became available, but a turbojet was incorporated into his original design to ensure that the tran­sition would not present any difficulties. At this time, the Shinden was known as the X-18.

By the time Tsuruno’s initial layout for the Shinden was complete the IJN had already issued its late 1943 18-shi specifications for three classes of aircraft. The first of these cov­ered an air superiority fighter (18-shi Ко), the second for an interceptor (18-shi Otsu) and the third for a night fighter (18-shi Hei). For the 18-shi Otsu competition, both Nakajima and Kawanishi had submitted designs: the single-engine J6K1 Jinpu (‘Squall’) and the twin-engine J5N1 Tenrai (or ‘Heavenly Thun­der’) respectively. These entries were based on the rather sparse directives of the specifi­cation which called for a top speed of 665km/h (413mph), a climb to 8,000m (26,246ft) in nine minutes and the ability to carry at least two 30mm cannons. To go with these two projects, Tsuruno introduced the Shinden to the IJN as a third competitor.

Despite some opposition to the design, the IJN was intrigued enough to accept the Shin­den proposal. However, the design had to show promise and the canard configuration needed to be proven before the IJN would authorise further development. Therefore, Tsuruno designed a glider based on his Shin­den concept as a means to test the canard properties and handling. Kugisho was com­missioned to build three gliders which were called the MXY6. Further details on MXY6 development can be found on page 69. The initial, positive results achieved with the MXY6 convinced the IJN to move forward with the Shinden project even before the completion of the glider testing by authorising two prototypes of the J7W1.

The IJN gave the Shinden project to Kyushu Нікбкі K. K. even though Kyushu had no expe­rience with high performance aircraft, let alone one like the Shinden. Unlike other major manufacturers however, Kyushu’s research facilities, personnel and production capacity were not heavily taxed by the needs of the Japanese war machine. To assist Kyushu, the IJN placed a team from the Dai – Ichi Kaigun Kokh Gijutsu-sho as well as Tsu­runo himself at the disposal of Kyushu engineers and managers to bolster their capability in handling the program.

With everything in position work com­menced on the first prototype in June 1944. The heart of the J7W1 was the Mitsubishi MK9D ([Ha-43]) 12 18-cylinder radial engine boosted by a supercharger. Although Tsuruno wanted to use a turbojet he rejected the Nel2B (TR-12) as insufficient in terms of thrust production. And since further turbojet developments were projected to show improved performance, the Shinden would use this radial engine until such time as a suit­able turbojet was available. The Mitsubishi engine and its supercharger were mounted in the rear of the fuselage. A six-bladed, metal Sumitomo VDM propeller was mated to the engine through an extension shaft and placed in a pusher configuration. If required the pro­peller could be jettisoned to effect pilot bail­out. On each side of the fuselage were air intakes for cooling the engine. The main wings were swept and on each was mounted a vertical stabiliser situated in approximately the middle of the wing. The pilot sat in a cock­pit in the centre of the fuselage while the canards were mounted on the nose. A tricy­cle landing gear was employed, the front tyre being 550x150mm and the two main tyres being 725x200mm in size.

The Shinden would carry four Type 5 30mm cannons. The Type 5, while heavier than the earlier Type 2 30mm gun, possessed a higher rate of fire at 500 rounds per minute and had a higher muzzle velocity. Each can­non was provided with 66 rounds. With less than eight seconds of 30mm rounds per gun, one hit would be sufficient to cripple and shoot down a fighter or bomber, therefore there was little ammunition to waste. There­fore, there were two Type 1 7.92mm machine guns, one on either side of the gun camera, in front of the nose. The purpose of these guns was not offensive but to serve as a ranging weapon for the cannons. Upon lining of his target, the pilot would fire a short burst from the machine guns. If the rounds struck the tar­get, he would fire a burst from the cannons and be reasonably assured of a hit, thereby conserving the precious cannon ammuni­tion. Each Type 1 was provided with 75 rounds of ammunition in a saddle dmm mag­azine. It should be noted that sources often list the two Type 1 weapons for training pur­poses, i. e. for practice and gunnery training, not gun laying. While certainly possible, gun laying would seem more plausible due to the rapid ammunition consumption of the Type 5 cannons and in training there is no real rea­son why machine guns would be used as a substitute for cannons. For payload, the Shin­den had a modest bomb carrying capacity of 120kg (2641b).

By September 1944, a model of the Shinden was being tested in a wind tunnel to assess its aerodynamic properties of the shape and planforms. With the results deemed accept­able, the first metal was cut on the prototype at the Kyushu Haruda factory located in Fukuoka City. By May 1945, the Shinden was nearly complete although it lacked the canopy, landing gear fairings, much of the main wings and other components. As the MK9D (I Ha-43 ]) 12 was already installed, test­ing of the powerplant commenced and trials showed that a cooling problem existed, prob­ably in part because no airflow was reaching the engine during static testing.

In June 1945, the first prototype was fin­ished but the armament was not fitted. Instead, weights simulating the Type 5 can­nons were installed in the nose. Flight testing was to commence immediately although the problem with the engine cooling would delay the first flight until 3 July. Tsuruno would be the first to fly the Shinden. The aircraft was to

MUNEO HOSAKA

PHOTOGRAPHS BY TIM HORTMAN

MUNEO HOSAKA

take-off from the Mushiroda Airport in Fukuoka City. The engine was started and Tsuruno climbed into the cockpit. On releas­ing the brakes and commencing to taxi, the Shinden showed an unexpected heavy torque pulling to the right. Surprised, Tsurano was unable to stop the plane swerving off the runway where the propeller touched the ground bending several of the blades by as much as 28cm (11 inches). In addition, a por­tion of the right wing’s vertical stabiliser was also damaged. The accident would delay flight testing for nearly a month while repairs were made. To prevent the propeller from striking the ground, tail wheels, as used on the Kyushu K11W Shiragiku trainer, were fit­ted to the bottom of the vertical stabilisers.

On 3 August 1945, the Shinden was pre­pared for flight. Only 38 litres (10 gallons) of fuel were loaded with 80 litres (21 gallons) of lubricating oil. The weights simulating the

Survivors

Kyushu J7W1 Shinden (FE-326)

This was the second Shinden prototype and was captured at Kyushu’s main factory. It was listed on the aviation industry release report on 10 March 1946 and to undergo restoration at MAMA by 1 August 1946. FE-326 was moved to Park Ridge in September 1946. Of note is the Shinden was provided with a stipulation that it should be housed in such a way that it could be quickly removed from storage if an engine and other parts were to be obtained to bring it to flight status. This never happened but the Shinden was fortunate enough to escape the cutting torch and was moved to the Paul. E. Garber facility where it currently remains in pieces and unrestored (see page 86).

cannons remained. The flight would be made by Kyushu’s Yoshitaka Miyaishi. With the torque now a known issue, Miyaishi was able to compensate and the Shinden successfully took to the air for the first time. The flight was for a very short duration and the aircraft was not taken above 400m (1,312ft). On landing Miyaishi reported that the take-off was rela­tively easy but rudder rise was experienced at 185km/h (115mph) with the plane lifting off the ground at 193km/h (120mph). As he climbed pushing the speed to 222km/h (138mph), the pull to the right caused by the torque from the propeller was very notice­able. After levelling off at 400m (1,312ft) and at a maximum speed of 161 mph, the pull was still a problem. He also found the landing to be a tricky process. The Shinden was found to have a relatively fast landing speed at 240km/h (149mph) and because of the torque pull and the inclination of the nose, bringing the Shinden down was not a simple task.

A second flight was made on 6 August 1945 with Miyaishi at the controls. Manoeuvrability was the main focus of the test, though the air­craft was flown up to 491 m (1,61 Oft). The pilot found that during the climb the nose wanted to dip. Again, the pull to the right was evident and during landing if a slight rudder up posi­tion was applied the nose would pop up just before touchdown. It was also discovered that the oil temperature rose as the flight went on and a means to rectify the problem would have to be found.

On 8 August 1945, the third and final flight of the Shinden took place with Miyaishi at the controls. At 193km/h (120mph), the nose wheel left the runway and at 203km/h (126mph) the plane lifted off. Miyaishi noted that the nose tended to drop regardless of how fast or slow the engine revolutions were. He also found that even with the nose down, the Shinden still flew horizontally with a level track and slight application of the rud­der. Landing speed was again 240km/h (149mph).

In total, the first Shinden logged between 30 and 45 minutes in the air. In addition to the problems already noted, Miyaishi com­plained of strong vibrations in the fuselage, in part due to the engine torque and from the extension shaft that mated the propeller to the engine. With the flight results, Kyushu engineers set about the process of solving the torque and vibration problems as well as the cooling concerns.

However, even before the Shinden took flight the IJN was desperately in need of a high performance interceptor. The Kawan – ishi J6K1 Jinpu failed to show any improve­ment over the Kawanishi N1K2-J Shiden-Kai

(meaning ‘Violet Lightning’, known to the Allies as George) and the Nakajima J5N1 Ten – rai was proving to be a disappointment by the time flight trials commenced in July 1944. With the failure of these two entries for the 18-shi specification, the IJN ordered the J7W1 Shinden into production in May 1944 and in so doing made the type the only canard configu­ration aircraft to achieve this status during World War 2. By September 1944, the pro­duction plans had been formulated with Kyushu’s Zasshonokuma factory expected to turn out 30 Shindens per month while Naka – jima’s Handa plant would produce 120 Shin­dens each month. In light of the war situation, such production numbers would have been very difficult to meet. As it was, the war ended before production could get going.

In addition to the first prototype, the second machine was also completed but it did not fly before the end of hostilities. The war’s end meant that the modifications required to cor­rect the problems found during ground and flight testing were never made. As a side note, nearly four decades later Colonel Bob Thacker would construct a radio controlled flying model of the Shinden. His initial proto­type showed the same pull problem as the original Shinden resulting in two crashes that required the complete rebuilding of the model each time. To solve this problem, Thacker placed the front canards at 7.5° pos­itive incidence, adjusted the centre of gravity and pointed the extension shaft for the pro­peller 3° to the right and 4.5° down from the zero thrust line. The pull problem was suc­cessfully eliminated by these adjustments and the Kyushu engineers may have found the same solution had they had the time to implement it.

The Shinden was not an easy aircraft to fly. Given the configuration of the aircraft, it would have required a skilled pilot to use in combat and Japan’s forces were low on experienced pilots by the time the Shinden would have entered service. The same prob­lem would plague the Germans when their high performance turbojet fighters were coming into operational use.

The end of the war also spelled the end of the J7W2 Shinden-Kai. This was to be the tur­bojet-equipped version of the Shinden. The use of the radial engine had been a stop gap until a suitable turbojet was available. The Ne 12B was rejected as its power was consid­ered too low to effectively propel the aircraft. In any case, work was by this time under way on the Kugisho Ne 20 turbojet that was based on the German BMW 003A engine, the only turbojet built and flown in a Japanese aircraft: the Nakajima Kitsuka (page 114). The J7W2 was to use the Ne 130 turbojet, also based on
the BMW 003A, which was being developed by Ishikawajima-Shibaura. The Ne 130 was to have produced nearly double the thrust of the Ne20; however, the Nel30 would not be ready by the close of the war and as such the J7W2 remained a design board aircraft. There is speculation concerning what the J7W2 would have looked like. One suggestion is that the J7W2 would have been the J7W1 with the Mitsubishi radial replaced with the Nel30 turbojet. A second suggestion con­cerns the fact that without the need for pro­

peller clearance the Shinden could dispense with the tall landing gear, thus lowering the height of the aircraft. Aside from modifying the landing gear, the vertical stabilisers, fuse­lage and canopy shape may also have required adjustment. It is likely that had development of the J7W2 commenced with the availability of the Ne 130, a J7W1 airframe would have been adapted to accept the engine and testing conducted on this, with other modifications coming into play as a pro­duction J7W2 was standardised.

Prior to the start of World War 2, there were men who foresaw the need for long range strategic bombers capable of striking across vast distances. Men like Generalleutnant Walter Wever of Germany who pushed with urgency the need for such bombers despite the veritable wall of opposition to such endeavours. This was also the case in Japan where it was clear that aggression against the United States would require the capability of hitting the US. Therefore in 1941, the Kaigun Koku Hombu issued its 16-shi specification for a long range bomber.

A review of bombers in service with the UN by 1941 showed that none were capable of crossing the Pacific to attack distant targets. At the time, the Mitsubishi G3M (codenamed Nell by the Allies) was being phased out to be replaced by the Mitsubishi G4M (known as Betty to the Allies and Hamaki or ‘Cigar’ to the Japanese). Although the G4M1 had a range of
6,043km (3,749 miles) this was insufficient to attack targets in the United States or, if required, deep into Russia. Following this review, the Kaigun Koku Hombu put forth the

16- shi specification for an attack bomber. Only two key specifications were stated. The first was that the maximum speed had to be at least 580km/h (361mph) and the second was a maximum range of at least 7,340km (4,598 miles). Mitsubishi set about the task of designing a bomber capable of meeting these requirements.

Initially, Mitsubishi engineer Kiro Honjo (who designed the G3M and G4M) proposed that the 16-shi bomber should be of a four engine design. Within Mitsubishi the bomber was known as the M-60. His pro­posal, however, was flatly rejected by the Kaigun Koku Hombu. Instead, another Mitsubishi engineer, Kijiro Takahashi, put for­ward his own design for the 16-shi bomber

which upon review was allowed to proceed.

Takahashi’s version of the M-60 was to use two ‘Nu’ engines. The Nu engine was a 24- cylinder, horizontal-H, liquid-cooled engine. Simply put, a horizontal-Н engine is two flat engines placed one on top of the other and geared together (a flat engine is one in which the pistons move horizontally). Despite hav­ing a poor power to weight ratio, they offer the advantage of being more compact and, because of this, Takahashi elected to use them on his bomber. Each engine was rated at 2,200hp at 5,000m (16,404ft).

In appearance, Takahashi’s bomber bore a strong resemblance to the Heinkel He 177 Greif (German for ‘Griffon’) heavy bomber that first flew on 19 November 1939. The nose

Mitsubishi G7M Taizan – data

Contemporaries

Bristol Buckingham (UK), Lockheed P2V Neptune (US), Junkers Ju 88H- 1 and H-2 (Germany), Junkers Ju 288A (Germany)

The specifications for the G7MI Taizan are based on the design dimensions and estimated performance of the final G7MI proposal as derived by Mitsubishi.

Type Long-Range Bomber

Crew Seven

Powerplant Two Mitsubishi MK10A (Ha-42-11) 18-cylinder, air­cooled radial engines developing 2,000hp for take-off, l,810hp at 2,200m (7,217ft) and 1,720hp at 5,400m (17,716ft); each engine drove a metal, four-bladed, alternating stroke propeller with a 4.5m (14.7ft) diameter Dimensions Span 25.00m 82.0ft Length 20.00m 65.611 Height 6.09m 20.0ft Wing area N/A Wing loading N/A Power loading 3.99kg/hp 8.8 lb/hp Weights Empty 10,600kg 23,3681b Loaded 16,000kg 35,2731b Useful load 5,400kg 11,9041b Bomb load 800kg 1,7641b maximum Performance Max speed 544km/h 344mph at 5,000m at 26,246ft Normal range 2,799km 1,739 miles Max range 7,400km 4,598 miles Climb 10 min to 10,000m (32,808ft) Ceiling N/A Fuel capacity 4,497 litres 1,188 gallons Armament Six 13mm Type 2 machine guns, two mounted in each of two upper fuselage turrets (one forward, one aft of the wings) and two in a ventral, rear firing position; two 20mm Type 99 Model 2 cannons, one mounted in the nose, the other in the tail